Method and apparatus for setting downlink control channel reception time in wireless communication system

ABSTRACT

Disclosed are a communication technique for merging, with IoT technology, a 5G communication system for supporting a data transmission rate higher than that of a 4G system, and a system therefor. The present disclosure can be applied to intelligent services (for example, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail, security, and safety-related services) on the basis of 5G communication technology and IoT-related technology. The present invention relates to a method and an apparatus for receiving a downlink control channel in a wireless communication system. Particularly, the present invention provides a method and an apparatus allowing a terminal to vary, according to base station settings or instructions, a reception time or reception timing, for a downlink control channel, transmitted from a base station.

TECHNICAL FIELD

The disclosure relates to a method and an apparatus for receivingdownlink control channel in a wireless communication system, and morespecifically to a method in which a terminal (UE) changes a receptiontime or reception timing of a downlink control channel transmitted froma base station according to configuration or indication of the basestation.

BACKGROUND ART

In order to meet wireless data traffic demands, which have increasedsince the commercialization of a 4G communication system, efforts todevelop an improved 5G communication system or a pre-5G communicationsystem have been made. For this reason, the 5G communication system orthe pre-5G communication system is called a beyond-4G-networkcommunication system or a post-LTE system. In order to achieve a highdata transmission rate, implementation of the 5G communication system inan mmWave band (for example, 60 GHz band) is being considered. In the 5Gcommunication system, technologies such as beamforming, massive MIMO,full-dimensional MIMO (FD-MIMO), array antennas, analog beam-forming,and large-scale antennas are being discussed as means to mitigate apropagation path loss in the mmWave band and increase a propagationtransmission distance. Further, in order to improve the system network,in the 5G communication system, development has progressed ontechnologies, such as an evolved small cell, an advanced small cell, acloud radio access network (cloud RAN), an ultra-dense network,device-to-device communication (D2D), a wireless backhaul, a movingnetwork, cooperative communication, coordinated multi-points (CoMP), andreception interference cancellation. In addition, in the 5G system,development has progressed on advanced coding modulation (ACM) schemessuch as hybrid FSK and QAM modulation (FQAM) and sliding windowsuperposition coding (SWSC), and advanced access technologies such asfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA).

Meanwhile, the Internet has evolved from a human-oriented connectionnetwork in which humans generate and consume information to anInternet-of-Things (IoT) network in which distributed components such asobjects exchange and process information. Internet-of-Everything (IoE)technology in which big-data processing technology through a connectionwith a cloud server or the like is combined with the IoT technology hasemerged. In order to implement the IoT, technical factors such as asensing technique, wired/wireless communication, network infrastructure,service-interface technology, and security technology are required, andresearch on technologies such as a sensor network, machine-to-machine(M2M) communication, machine-type communication (MTC), and the like forconnection between objects has recently been conducted. In an IoTenvironment, through collection and analysis of data generated inconnected objects, an intelligent Internet technology (IT) service tocreate new value for peoples' lives may be provided. The IoT may beapplied to fields, such as a smart home, a smart building, a smart city,a smart car, a connected car, a smart grid, health care, smart homeappliances, or a high-tech medical service, through convergence betweenthe conventional information technology (IT) and various industries.

Accordingly, various attempts to apply a 5G communication system to theIoT network are being made. For example, 5G communication technology,such as a sensor network, machine-to-machine (M2M) communication, andmachine-type communication (MTC), has been implemented using techniquessuch as beamforming, MIMO, and array antennas. The application of acloud RAN as big-data processing technology described above may be anexample of convergence of 5G technology and IoT technology.

In the 5G system, it is possible to transmit or receive a signal to orfrom a UE by using an unlicensed band. Whether to use the unlicensedband is determined based on whether the unlicensed band is idle.Specifically, when downlink transmission is performed in an unlicensedband or by a cell or base station operating in the unlicensed band, thebase station performs a channel access procedure or a listen-before-talk(LBT) for the unlicensed band, in which the downlink transmission hasbeen configured, in advance of or immediately before a configureddownlink transmission start time point. When the unlicensed band isdetermined to be idle as a result of performing the channel accessprocedure, the base station may perform the downlink signaltransmission. Meanwhile, when the unlicensed band is determined not tobe idle according to the channel access procedure performed by the basestation, the base station cannot perform the configured downlink signaltransmission.

Therefore, it is preferable that the base station transfer a downlinksignal (e.g. downlink control information (DCI) includinguplink/downlink resource allocation information) to the UE immediatelywhen the unlicensed band is determined to be idle after the channelaccess procedure is performed. To this end, the UE configured totransmit or receive a signal in the unlicensed band very frequentlyreceives downlink control information transmitted by the base station,and must always determine, from the received downlink controlinformation, whether uplink/downlink resource allocation information ofthe UE has been transferred. When the UE frequently receives or detectsthe downlink control information, the UE unnecessarily consumes power inreceiving and decoding the downlink control information, and thus theperformance thereof may be degraded. Therefore, there is the need for amethod for adaptively adjusting the downlink control informationreception time or period of the UE according to the result of performingthe channel access procedure.

DISCLOSURE OF INVENTION Technical Problem

The disclosure proposes an apparatus and a method wherein a UE receives,from a base station, configuration for one or more downlink controlinformation reception times or periods, or an instruction orreconfiguration for at least one time or period among the downlinkcontrol information reception times or periods.

Solution to Problem

In order to solve the above-described problems, the disclosure providesa method of a UE in a wireless communication system, the methodincluding: monitoring a downlink control channel in an unlicensed band,based on a first period for the downlink control channel; when firstdownlink control information is received based on the first period,monitoring the downlink control channel, based on a second period forthe downlink control channel; and receiving second downlink controlinformation, based on the first downlink control information, whereinthe first downlink control information relates to an occupancy intervalof a base station. Further, the first downlink control information mayinclude at least one of multiple slot format indicators and informationon a downlink transmission interval and an uplink transmission interval.The second downlink control information may be UE-specific controlinformation. The period for the downlink control channel may beconfigured by higher-layer signaling, and the first control informationmay include information on the second period for the downlink controlchannel.

Further, a method of a base station in a wireless communication systemincludes: performing a channel access procedure in an unlicensed band;when the unlicensed band is found to be idle as a result of the channelaccess procedure, transmitting first downlink control information byusing the unlicensed band on a downlink control channel, based on afirst period for the downlink control channel; and transmitting seconddownlink control information by using the unlicensed band, based on asecond period for the downlink control channel, wherein the firstdownlink control information relates to an occupancy interval of thebase station.

Further, a UE in a wireless communication system includes: atransceiver; and a controller connected to the transceiver andconfigured to: monitor a downlink control channel in an unlicensed band,based on a first period for the downlink control channel; when firstdownlink control information is received based on the first period,monitor the downlink control channel, based on a second period for thedownlink control channel; and receive second downlink controlinformation, based on the first downlink control information, whereinthe first downlink control information relates to an occupancy intervalof a base station.

Further, a base station in a wireless communication system includes: atransceiver; and a controller connected to the transceiver andconfigured to: perform a channel access procedure in an unlicensed band;when the unlicensed band is found to be idle as a result of the channelaccess procedure, transmit first downlink control information by usingthe unlicensed band on a downlink control channel, based on a firstperiod for the downlink control channel; and transmit second downlinkcontrol information by using the unlicensed band, based on a secondperiod for the downlink control channel, wherein the first downlinkcontrol information relates to an occupancy interval of the basestation.

Advantageous Effects of Invention

According to an embodiment of the disclosure, a UE receives, from a basestation, configuration for one or more downlink control informationreception times or periods, or receives an instruction orreconfiguration for at least one time or period among the downlinkcontrol information reception times or periods. Therefore, the UE canchange the configured downlink control information reception time orperiod and receive control information, and thus can minimize theconsumption of power by the UE in receiving downlink controlinformation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a downlink time-frequency domain transmissionstructure of an LTE or LTE-A system;

FIG. 2 illustrates an uplink time-frequency domain transmissionstructure of an LTE or LTE-A system;

FIG. 3 illustrates an example in which data for eMBB, URLLC, and mMTC ina communication system are allocated from a frequency-time resource;

FIG. 4 illustrates a downlink control channel reception time or periodof a base station and a UE;

FIG. 5 illustrates an example of a downlink control channel receptiontime or period of a base station and a UE of the disclosure;

FIG. 6 illustrates another example of a downlink control channelreception time or period of a base station and a UE of the disclosure;

FIG. 7 illustrates another example of a downlink control channelreception time or period of a base station and a UE of the disclosure;

FIG. 8 is flowchart illustrating an operation of a base stationaccording to embodiments of the disclosure;

FIG. 9 is flowchart illustrating an operation of a UE according toembodiments of the disclosure;

FIG. 10 is a block diagram illustrating a structure of a base stationaccording to embodiments of the disclosure; and

FIG. 11 is a block diagram illustrating a structure of a UE according toembodiments of the disclosure.

MODE FOR THE INVENTION

In describing the embodiments of the disclosure, descriptions related totechnical contents which are well-known in the art to which thedisclosure pertains, and are not directly associated with thedisclosure, will be omitted. Such an omission of unnecessarydescriptions is intended to prevent obscuring of the main idea of thedisclosure and to more clearly transfer the main idea.

For the same reason, in the accompanying drawings, some elements may beexaggerated, omitted, or schematically illustrated. Further, the size ofeach element may not accurately reflect the actual size. In thedrawings, identical or corresponding elements are provided withidentical reference numerals.

The advantages and features of the disclosure and methods of achievingthe same will be made apparent by referring to the embodiments describedbelow in detail in conjunction with the accompanying drawings. However,the disclosure is not limited to the embodiments set forth below, andmay be implemented in various different forms. The following embodimentsare provided only to make the disclosure complete and completely informthose skilled in the art to which the disclosure belongs of the scope ofthe disclosure. The disclosure is defined only by the scope of theclaims. Throughout the specification, the same reference numeralsdesignate the same elements.

Here, it will be understood that each block of the flowchartillustrations and a combination of the flowchart illustrations can becarried out by computer program instructions. These computer programinstructions can be provided to a processor of a general-purposecomputer, special-purpose computer, or other programmabledata-processing apparatus to produce a machine. Thus, the instructions,which are executed via the processor of the computer or otherprogrammable data-processing apparatus, create means for performing thefunctions specified in the flowchart block(s). These computer programinstructions may also be stored in a computer-usable orcomputer-readable memory that can direct a computer or otherprogrammable data-processing apparatus to function in a particularmanner. Thus, the instructions stored in the computer-usable orcomputer-readable memory may produce an article of manufacture includinginstruction means that perform the function specified in the flowchartblock(s). The computer program instructions may also be loaded onto acomputer or other programmable data-processing apparatus to cause aseries of operational steps to be performed on the computer or otherprogrammable data-processing apparatus to produce a computer-implementedprocess such that the instructions executed on the computer or otherprogrammable data-processing apparatus provide steps for implementingthe functions specified in the flowchart block(s).

Further, each block of the flowchart illustrations may represent amodule, a segment, or a portion of code that includes one or moreexecutable instructions for executing the specified logical function(s).It should also be noted that in some alternative implementations, thefunctions noted in the blocks may occur out of the order. For example,two blocks shown in succession may in fact be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

The term “unit” used in the present embodiment refers to a softwareelement or a hardware element, such as an FPGA or an ASIC, whichperforms a predetermined function. However, “unit” does not always havea meaning limited to software or hardware. The “unit” may be configuredeither to be stored in an addressable storage medium or to reproduce oneor more processors. Therefore, the “unit” includes, for example,elements such as software elements, object-oriented software elements,class elements and task elements, processes, functions, properties,procedures, sub-routines, segments of program code, drivers, firmware,micro-code, circuits, data, databases, data structures, tables, arrays,and parameters. The elements and functions provided by the “unit” mayalso be combined into a smaller number of elements and “units” or may bedivided into a larger number of elements and “units”. Moreover, theelements and “units” may be implemented to reproduce one or more CPUswithin a device or a security multimedia card. Also, in an embodiment,the “unit” may include one or more processors.

A wireless communication system has developed into a broadband wirelesscommunication system that provides a high-speed and high-quality packetdata service, such as the communication standards, for example,high-speed packet access (HSPA) of 3GPP, long-term evolution (LTE) orevolved universal terrestrial radio access (E-UTRA), LTE-advanced(LTE-A), high-rate packet data (HRPD) of 3GPP2, ultra-mobile broadband(UMB), and IEEE 802.16e, beyond the initially provided voice-basedservice. Further, communication standards for 5G or new radio or nextradio (NR), which is a fifth-generation wireless communication system,are being made.

As described above, in a wireless communication system including afifth-generation system, at least one service among enhanced mobilebroadband (eMBB), massive machine-type communications (mMTC), andultra-reliable and low-latency communications (URLLC) may be provided toa UE. The above services may be provided to the same UE during the sametime interval. In the present embodiment, eMBB may be a service forhigh-speed transmission of high-volume data, mMTC may be a service forUE power minimization and connection of multiple UEs, and URLLC may be aservice for high reliability and low delay, but the services are notlimited thereto. The three services may be important scenarios in an LTEsystem or a 5G or NR system after LTE.

Hereinafter, an embodiment of the disclosure will be described in detailwith reference to the accompanying drawings. In the followingdescription of the disclosure, a detailed description of known functionsor configurations incorporated herein will be omitted when it may makethe subject matter of the disclosure rather unclear. The terms whichwill be described below are terms defined in consideration of thefunctions in the disclosure, and may differ according to users,intentions of the users, or customs. Therefore, the definitions of theterms should be made based on the content throughout the specification.

Hereinafter, a base station is a subject for performing resourceallocation for a UE, and may be at least one among eNode B, Node B, abase station (BS), a wireless connection unit, a base stationcontroller, or a node on a network. A UE may include user equipment(UE), a mobile station (MS), a cellular phone, a smartphone, a computer,or a multimedia system capable of performing a communication function.In the disclosure, a downlink (DL) is a wireless transmission path of asignal which a base station transmits to a UE, and an uplink (UL) is awireless transmission path of a signal which a UE transmits to a basestation.

Hereinafter, an embodiment of the disclosure will be described as anexample of an LTE or LTE-A system. However, the embodiment of thedisclosure may be applied to other communication systems having asimilar technical background or channel form. For example,fifth-generation mobile communication technologies (5G, new radio, NR)may be included herein. Further, the embodiment of the disclosure may beapplied to other communication systems through some modificationsaccording to the determination of those skilled in the art withoutlargely deviating from the scope of the disclosure.

An LTE system, which is a representative example of the broadbandwireless communication system, adopts an orthogonal frequency-divisionmultiplexing (OFDM) method in a downlink and a single carrierfrequency-division multiple access (SC-FDMA) method in an uplink. Inmultiple access methods as described above, data or control informationof each user is classified by assigning and operating time-frequencyresources for carrying data or control information for each user suchthat the time-frequency resources do not overlap each other, that is,such that orthogonality is established.

The LTE system employs a hybrid automatic repeat request (HARQ) methodof retransmitting the corresponding data in a physical layer whendecoding fails upon the initial transmission. When a receiver fails toaccurately decode data, the HARQ method enables the receiver to transmitinformation for providing notification of the decoding failure (negativeacknowledgement (NACK)) to a transmitter so that the transmitter canretransmit the corresponding data in a physical layer. The receiver maycombine the data retransmitted by the transmitter with data that failedto be decoded, thereby increasing data reception performance. Further,when the receiver accurately decodes data, the receiver transmitsinformation (acknowledgement (ACK)) reporting that decoding wassuccessfully executed, so that the transmitter transmits new data.

FIG. 1 illustrates a basic structure of time-frequency domain, which isa radio resource domain in which data or a control channel istransmitted in a downlink of an LTE or LTE-A system.

Referring to FIG. 1, the horizontal axis represents the time domain andthe vertical axis represents the frequency domain. The minimumtransmission unit in the time domain is an OFDM symbol. N_(symbol) OFDMsymbols 120 constitute one slot 106, and two slots form one subframe105. The length of the slot is 0.5 ms and the length of the subframe is1.0 ms. A radio frame 114 is a time-domain interval including tensubframes. The minimum transmission unit in the frequency domain is asubcarrier, and the entire system transmission bandwidth includes atotal of N_(BW) subcarriers 104. However, such specific values may bevariably applied.

In a time-frequency domain, the basic unit of a resource is a resourceelement (RE) 112, which may be represented by an OFDM symbol index and asubcarrier index. A resource block (RB) or physical resource block (PRB)108 is defined as N_(symb) consecutive OFDM symbols 102 in the timedomain and N_(RB) consecutive subcarriers 110 in the frequency domain.Thus, one RB 108 in one slot may include N_(symb)×N_(RB) REs 112. Ingeneral, the minimum allocation unit of data in the frequency domain isthe RB 108. In the LTE system, in general, N_(symb)=7 and N_(RB)=12, andN_(BW) may be proportional to a system transmission bandwidth. The datarate increases in proportion to the number of RBs scheduled to a UE. TheLTE system can define and operate six transmission bandwidths.

In the case of a frequency-division duplexing (FDD) system in which thedownlink and the uplink are separated by frequency and are operated, thedownlink transmission bandwidth and the uplink transmission bandwidthmay be different from each other. A channel bandwidth indicates an RFbandwidth corresponding to a system transmission bandwidth. Table 1,provided below, shows the relationship between a system transmissionbandwidth and a channel bandwidth defined in the LTE system. Forexample, an LTE system having a 10 MHz channel bandwidth may have atransmission bandwidth of 50 RBs.

TABLE 1 Channel Bandwidth BW_(channel) [MHz] 1.4 3 5 10 15 20Transmission 6 15 25 50 75 100 bandwidth configuration N_(RB)

Downlink control information may be transmitted within the first N OFDMsymbols in the subframe. In the present embodiment, N={1, 2, 3} ingeneral. Therefore, the value of N can be variably applied to eachsubframe according to the amount of control information to betransmitted in the current subframe. The control information to betransmitted may include a control channel transmission intervalindicator indicating the number of OFDM symbols at which controlinformation is transmitted, scheduling information for downlink data oruplink data, and HARQ ACK/NACK information.

In the LTE system, the scheduling information for downlink data oruplink data may be transmitted from a base station to a UE throughdownlink control information (DCI). DCI is defined according to variousformats, and may indicate, according to each format, whether DCI isscheduling information (UL grant) for uplink data or schedulinginformation (DL grant) for downlink data, whether DCI is compact DCIhaving a small size of control information, whether to apply spatialmultiplexing using multiple antennas, whether or not DCI is used forpower control, and the like. For example, DCI format 1, which is thescheduling control information (DL grant) for downlink data, may includeat least one of the following types of control information.

Resource allocation type 0/1 flag: Indicates whether a resourceallocation type is type 0 or type 1. Type 0 allocates resources in unitsof resource block groups (RBG) by applying a bitmap scheme. In the LTEsystem, the basic unit of scheduling is an RB, represented by time andfrequency domain resources, and an RBG includes multiple RBs and becomesthe basic unit of scheduling in the type 0 scheme. Type 1 allows aspecific RB to be allocated within the RBG.

Resource block assignment: Indicates an RB allocated to datatransmission. The resources to be represented are determined accordingto a system bandwidth and a resource allocation scheme.

Modulation and coding scheme (MCS): Indicates the modulation scheme usedfor data transmission and the size of the transport block to betransmitted.

HARQ process number: Indicates the process number of HARQ.

New data indicator: Indicates whether HARQ is initial transmission orretransmission.

Redundancy version: Indicates the redundancy version of HARQ.

Transmit power control (TPC) command for physical uplink control channel(PUCCH): Indicates a transmit power control command for a PUCCH which isan uplink control channel.

The DCI undergoes channel coding and modulation and may then betransmitted on a physical downlink control channel (PDCCH) or anenhanced PDCCH (EPDCCH), which is a downlink physical control channel.Hereinafter, PDCCH transmission/reception and DCI transmission/receptionon PDCCH may be used together. Similarly, downlink datatransmission/reception and physical downlink shared channel (PDSCH)transmission/reception may be used together. Also, uplink datatransmission/reception and physical uplink shared channel (PUSCH)transmission/reception may be used together.

Generally, the DCI is scrambled with a predetermined radio networktemporary identifier (RNTI) (or a UE identifier), independently for eachUE, a cyclic redundancy check (CRC) is added, and channel coding isperformed, whereby each independent PDCCH is configured and transmitted.In the time domain, the PDCCH is mapped and transmitted during thecontrol channel transmission interval. The frequency-domain mappingposition of the PDCCH may be determined by the ID of each UE, and may bespread over the entire system transmission band.

Downlink data may be transmitted on PDSCH, which is a physical channelfor downlink data transmission. The PDSCH may be transmitted after thecontrol channel transmission interval, and scheduling information suchas a specific mapping position and a modulation scheme in the frequencydomain is determined based on the DCI transmitted through the PDCCH.

A base station notifies a UE of the modulation scheme applied to a PDSCHto be transmitted and a transport block size (TBS), which is the size ofdata to be transmitted, through MCS among control informationconstituting the DCI. In the embodiment, the MCS may include 5 bits, orlarger or smaller number of bits. The TBS corresponds to a size beforechannel coding for error correction is applied to data (TB) to betransmitted by the base station.

The modulation schemes supported by the LTE system are quadraturephase-shift keying (QPSK), 16 quadrature amplitude modulation (16 QAM),and 64 QAM, and modulation orders (Q_(m)) thereof correspond to 2, 4,and 6, respectively. That is, it is possible to transmit 2 bits persymbol for QPSK modulation, 4 bits per symbol for 16 QAM modulation, and6 bits per symbol for 64 QAM modulation. In addition, modulation of 256QAM or higher may be used according to the system modification.

FIG. 2 illustrates a basic structure of a time-frequency domain, whichis a radio resource domain in which data or a control channel istransmitted in an uplink of an LTE or LTE-A system.

Referring to FIG. 2, the horizontal axis represents a time domain andthe vertical axis represents a frequency domain. The minimumtransmission unit in the time domain is an SC-FDMA symbol, and N_(symb)SC-FDMA symbols 202 may form one slot 206. Then, two slots form onesubframe 205. The minimum transmission unit in the frequency domain is asubcarrier, and the entire system transmission bandwidth includes atotal of N_(BW) subcarriers 204. N_(BW) may have a value proportional tothe system transmission bandwidth.

The basic unit of resources in the time-frequency domain is a resourceelement (RE) 212, which can be defined as an SC-FDMA symbol index and asubcarrier index. A resource block (RB) 208 may be defined as N_(symb)consecutive SC-FDMA symbols in the time domain and N_(RB) consecutivesubcarriers in the frequency domain. Therefore, one RB includesN_(symb)×N_(RB) REs. In general, the minimum transmission unit of dataor control information is an RB unit. A PUCCH is mapped to a frequencydomain corresponding to one RB and is transmitted for one subframe.

In the LTE system, it is possible to define the transmission timingrelationship between a PDSCH or a PDCCH or EPDDCH including asemi-persistent scheduling release (SPS release), which is a downlinkdata transmission physical channel, and a PUCCH or PUSCH, which is anuplink physical channel on which HARQ ACK/NACK corresponding to thePDCCH or EPDDCH is transmitted. For example, in an LTE system operatingaccording to FDD, an HARQ ACK/NACK, corresponding to a PDCCH or EPDCCHincluding an SPS release or a PDSCH, transmitted in an (n-4)th subframemay be transmitted on a PUCCH or a PUSCH in an nth subframe.

In the LTE system, a downlink HARQ employs an asynchronous HARQ schemein which the data retransmission time point is not fixed. That is, whena station receives feedback of an HARQ NACK from a UE with respect todata initially transmitted by the base station, the base station freelydetermines, through a scheduling operation, the transmission time pointof data to be retransmitted. For an HARQ operation, the UE may bufferdata determined to be erroneous as a result of decoding of the receiveddata and perform combining with the data retransmitted from the basestation.

The HARQ ACK/NACK information of PDSCH transmitted in subframe n-k maybe transmitted from a UE to a base station through a PUCCH or PUSCH insubframe n. Here, k may be defined differently depending on FDD or timedivision duplex (TDD) of the LTE system and on the subframeconfiguration. For example, in the case of the FDD LTE system, k isfixed to 4. On the other hand, in the case of the TDD LTE system, k maybe changed according to a subframe configuration and a subframe number.Also, the value of k may be applied differently depending on the TDDconfiguration of each carrier at the time of data transmission throughmultiple carriers. In the case of TDD, the value of k is determineddepending on TDD UL/DL configuration, as shown in Table 2.

TABLE 2 UL-DL Subframe n configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 —— 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, 4, 6— — 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 6, 5, — — — — — — 7,11, 4, 7 5 — — 13, 12, 9, — — — — — — — 8, 7, 5, 4, 11, 6 6 — — 7 7 5 —— 7 7 —

In the LTE system, unlike downlink HARQ, uplink HARQ adopts asynchronous HARQ scheme in which the data transmission time point isfixed. That is, the uplink/downlink timing relationship among a PUSCH,which is a physical channel for uplink data transmission, a PDCCH, whichis a downlink control channel preceding the PUSCH, and a physical hybridindicator channel (PHICH), which is a physical channel on which HARQACK/NACK corresponding to the PUSCH is transmitted, may be determined bythe following rule.

When the UE receives a PDCCH including uplink scheduling controlinformation transmitted from the base station in subframe n or a PHICHin which downlink HARQ ACK/NACK is transmitted, the UE transmits uplinkdata corresponding to the control information through a PUSCH insubframe n+k. Here, k may be defined differently depending on FDD or TDDof the LTE system and on the configuration thereof. For example, in thecase of an FDD LTE system, k may be fixed to 4. On the other hand, inthe case of a TDD LTE system, k may be changed according to a subframeconfiguration and a subframe number. Also, the value of k may be applieddifferently depending on the TDD configuration of each carrier at thetime of data transmission through multiple carriers. In the case of theTDD, the value of k is determined according to a TDD UL/DL configurationas in Table 3.

TABLE 3 TDD UL/DL subframe index n configuration 0 1 2 3 4 5 6 7 8 9 0 46 4 6 1 6 4 6 4 2 4 4 3 4 4 4 4 4 4 5 4 6 7 7 7 7 5

HARQ-ACK information of a PHICH to be transmitted in subframe i isassociated with a PUSCH transmitted in subframe i-k. In the FDD system,k is provided as 4. That is, in the FDD system, HARQ-ACK information ofthe PHICH to be transmitted in subframe i is associated with a PUSCHtransmitted in subframe i-4. In the case of the TDD system, when onlyone serving cell is configured for a UE in which enhanced interferencemitigation and traffic adaptation (EIMTA) is not configured, or whenmultiple cells are all configured through the same TDD UL/DLconfiguration, in the TDD UL/DL configuration 0 to 6, the value of k maybe provided according to Table 4 below.

TABLE 4 TDD UL/DL subframe index n configuration 0 1 2 3 4 5 6 7 8 9 0 74 7 4 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 6 4 7 4 6

For example, when TDD UL/DL configuration 1 is applied, a PHICH to betransmitted in subframe 6 may be HARQ-ACK information of a PUSCHtransmitted in subframe 2 which is ahead by four subframes.

In the case of TDD UL/DL configuration 0, when HARQ-ACK is received in aPHICH resource corresponding to I_(PHICH)=0, the PUSCH indicated by theHARQ-ACK information is a channel transmitted in subframe i-k, and thevalue of k is provided according to Table 4. In the case of TDD UL/DLconfiguration 0, when HARQ-ACK is received as a PHICH resourcecorresponding to I_(PHICH) =1, the PUSCH indicated by the HARQ-ACKinformation is a channel transmitted in subframe i-6.

In the case of an LTE system that performs downlink or uplinkcommunication in an unlicensed band (hereinafter, referred to as alicensed assisted access (LAA) system), a base station or a UE shoulddetermine, before the transmission of a downlink or uplink signal, theidle state of an unlicensed band in which communication is performed.For example, when the size of a signal received in the unlicensed bandis smaller than a specific threshold value for a predetermined period oftime, the base station or the UE may perform signal transmission to theunlicensed band. Accordingly, when the UE transmits an uplink signal inthe LAA system, the base station determines the idle state of theunlicensed band, and when the unlicensed band is determined to be idle,the base station may transmit, to the UE, a PDCCH including uplinkscheduling control information for configuring uplink data transmissionof the UE.

The description of the wireless communication system is based on an LTEsystem, but the content of the disclosure is not limited to the LTEsystem, and may be applied to various wireless communication systemssuch as NR and 5G. Also, when the embodiment is applied to wirelesscommunication systems other than LTE, the value of k may be changed andapplied to a system using a modulation scheme corresponding to FDD.

FIG. 3 illustrates an example in which data for eMBB, URLLC, and mMTC,which are services considered in a 5G or NR system, are allocated infrequency-time resources.

Referring to FIG. 3, it can be found that a scheme is depicted in whichfrequency and time resources are allocated for information transmissionin each system. eMBB, URLLC, and mMTC data are allocated in the entiresystem frequency band 300. When URLLC data 303, 305, and 307 aregenerated while eMBB data 301 and mMTC data 309 are allocated andtransmitted in a specific frequency band, and thus transmission of thegenerated URLLC data is necessary, a transmitter may empty a part inwhich the eMBB data 301 and the mMTC data 309 have already beenallocated, and may then transmit the URLLC data 303, 305, and 307, ormay transmit the URLLC data 303, 305, and 307 without performingscheduled transmission. Among the above services, since URLLC requires areduced delay time, URLLC data may be allocated (303, 305, and 307) to aportion of the resource 301 to which the eMBB is allocated, and may betransmitted. Of course, when URLLC is additionally allocated andtransmitted in the resource to which the eMBB is allocated, the eMBBdata may not be transmitted in the overlapping frequency-time resource,and thus the transmission performance of the eMBB data may be lowered.That is, in the above case, eMBB data transmission failure due to URLLCallocation may occur.

Generally, the length of a transmission time interval (TTI) used forURLLC transmission may be shorter than the length of a TTI used for eMBBor mMTC transmission. Further, a transmitter may transmit a response toinformation related to the URLLC faster than eMBB or mMTC, and thusinformation may be transmitted or received with a low delay.

The structure of a physical layer channel used for each type to transmitthe three types of services or data may be different. For example, atleast one among the length of a TTI, subcarrier spacing, the allocationunit of frequency resources, the structure of a control channel, and themethod of mapping data may be different.

In the above description, three types of services and three types ofdata have been described. However, more types of services and datacorresponding thereto may exist, in which case the content of thedisclosure may also be applied.

The terms, physical channel and signal in the conventional LTE or LTE-Asystem, may be used to describe the method and apparatus proposed by theembodiment. However, the content of the disclosure may be applied towireless communication systems other than LTE and LTE-A systems.

In the disclosure, higher-layer signaling or a higher-layer signal is asignal transmission method in which a signal is transmitted from a basestation to a UE by using a downlink data channel of a physical layer orfrom a UE to a base station by using an uplink data channel of aphysical layer, and includes RRC signaling, PDCP signaling, or a signaltransmission method in which a signal is transmitted through a MACcontrol element (MAC CE).

The content of the disclosure is described with reference to a LAAsystem, but may also be applicable to an FDD system, a TDD system, andan NR system. In addition, the content of the disclosure may beapplicable to a standalone system operating only in the unlicensed bandwithout the assistance of the licensed band.

When downlink transmission is performed in an unlicensed band or from acell or a base station operating in an unlicensed band, the base stationperforms a channel access procedure (or listen-before talk (LBT)) forthe unlicensed band, in which a downlink signal is desired to betransmitted, before or immediately before the start of downlink signaltransmission. When it is determined in the performed channel accessprocedure that the unlicensed band is idle, the base station may performthe downlink signal transmission. Meanwhile, when it is determined thatthe unlicensed band is not idle according to the channel accessprocedure performed by the base station, the base station cannot performthe downlink signal transmission.

In the channel access procedure in the unlicensed band in which thedownlink transmission is established, the base station generallydetermines an idle state of the unlicensed band by comparing theintensity of a signal received for a predetermined time with apredefined threshold value or a threshold value calculated by a functionincluding at least one variable among a channel bandwidth, a signalbandwidth at which a signal to be transmitted is transmitted, theintensity of transmission power, the beam width of a transmissionsignal, etc.

For example, when the intensity of a signal received for 25 us is lessthan a predefined threshold value of −72 dBm, the base station maydetermine that the unlicensed band is idle and may perform downlinktransmission. At this time, the maximum possible time of the downlinksignal transmission may be limited according to a maximum channeloccupancy time defined for each country and region in the unlicensedband. For example, in Japan, in a 5 GHz unlicensed band, a base stationor a UE can transmit a signal by occupying the channel for a maximum of4 ms after the channel access procedure is performed. When the intensityof a signal received for 25 us is greater than a predefined threshold of−72 dBm, the base station determines that the unlicensed band is notidle and does not perform the downlink transmission.

FIG. 4 illustrates a downlink control channel reception time or periodof a base station and a UE. The following detailed description will bemade with reference to FIG. 4.

The UE receives a configuration for a time or period (e.g., every slotor every subframe 450, 452, 454, and 456 or period thereof 460), duringwhich the UE must receive the downlink control channel, from the basestation through a higher-layer signal. In this case, the time or periodduring which the UE receives the downlink control channel may beconfigured according to downlink control information (DCI or DCIformats) transmitted through the downlink control channel and accordingto the time and frequency location (a search space or a control resourceset (CORESET)) in which the downlink control channel is transmitted. Apart of the time or period during which the UE receives the downlinkcontrol channel may be defined in advance between the base station andthe UE.

The UE, having received the configuration for a downlink control channelreception time or period as described above, receives a downlink controlchannel according to the configured time or period. When the basestation transmits downlink control information (DCI) to the UE throughthe received downlink control channel, the UE may receive, in the timeand frequency domain configured in the received downlink controlinformation, the downlink control information (e.g., at least onedownlink signal among a channel-state information reference signal(CSI-RS), a physical broadcast channel (PBCH), or a physical downlinkshared channel (PDSCH)), or may transmit, to the base station, uplinkcontrol information (e.g. at least one uplink signal among a soundingreference signal (SRS), uplink control information (UCI), a physicalrandom access channel (PRACH), a PUCCH, or a PUSCH). In other words, inaccordance with a downlink control channel reception time or periodconfigured for a UE, a base station may transmit downlink controlinformation (for establishing downlink signal reception or uplink signaltransmission) to the UE, and the UE may receive a downlink controlchannel from the base station according to the configured downlinkcontrol channel time or period to thereby receive the downlink controlinformation.

Hereinafter, an example of an operation of a base station and a UEcommunicating with each other using an unlicensed band will bedescribed. The base station determines that downlink signal transmissionis necessary for the UE, and transmits downlink control information tothe UE according to the downlink control channel reception time orperiod of the UE. In order to transmit the downlink control information,the base station performs, before a downlink control channel receptiontime 450 or period of the UE, a channel access procedure 420 for anunlicensed band which the base station desires to use for transmitting adownlink signal to the UE. In the disclosure, since the channel accessprocedure of the base station or the UE is not related to the problem tobe solved in the disclosure, a detailed description of the channelaccess procedure is omitted in the disclosure.

When a base station determines that the unlicensed band is idle, thebase station may transmit a downlink signal or may receive an uplinksignal from at least one UE for the maximum channel occupancy time 410through the unlicensed band. The maximum channel occupancy time (or themaximum channel occupancy interval) in which the base station and the UEcan transmit signals through the unlicensed band may be defineddifferently for each country and region. For example, in Japan, a basestation or a UE in a 5 GHz unlicensed band can transmit a signal whileoccupying the channel for a maximum time of 4 ms after performing achannel access procedure. A base station or UE that has occupied or usedthe unlicensed band during the maximum channel occupancy time must againperform the channel access procedure for the unlicensed band.

When a time 430, at which the base station determines that theunlicensed band is idle through the performance of a channel accessprocedure, precedes the time 450 at which the UE receives a downlinkcontrol channel, the base station may occupy the unlicensed band untilthe time 450, at which the UE receives the downlink control channel, bytransmitting a specific signal 440 (e.g., a reservation signal) untilthe downlink control channel reception time of the UE. The specificsignal may be a signal arbitrarily generated by the base station or asignal defined in advance between the base station and the UE. Also, theUE may not receive the specific signal.

When the base station transmits, as described above, a specific signalto occupy an unlicensed band, the transmission time of the specificsignal is also included in the maximum channel occupancy time. When theUE does not receive the specific signal, the specific signaltransmission is unnecessary signal transmission. Therefore, the basestation preferably minimizes the transmission time of the specificsignal. However, since the base station cannot know, in advance, theresult of performing the channel access procedure, the specific signaltransmission may be inevitable. In order to solve this problem, the basestation configures the UE to very frequently receive downlink controlinformation (for example, the base station may configure the UE toreceive downlink control information every N symbols (N≥1), therebyminimizing the transmission time of the specific signal. For example,the base station configures the UE to receive downlink controlinformation in each symbol and performs the channel access procedure,and then, immediately after the unlicensed band is determined to beidle, transmits a downlink signal (e.g. downlink control informationincluding uplink/downlink resource allocation information) to the UE,and thus may not transmit the specific signal or may minimize thetransmission time of the specific signal.

However, the UE configured to transmit or receive a signal in theunlicensed band very frequently receives downlink control informationtransmitted from a base station and must detect or determine every time,from the received downlink control information, that uplink/downlinkresource allocation information or uplink/downlink schedulinginformation configured by the base station has been transmitted to theUE. As described above, when the UE frequently performs downlink controlinformation reception and detection, the UE consumes excessive power toreceive and decode the downlink control information and thus theperformance of the UE may be lowered. Therefore, there is a need for amethod of minimizing unnecessary downlink signal reception and detectionof the UE while minimizing the transmission of the specific signal.

Hereinafter, embodiments of the disclosure will be described under theassumption that the period of time during which the UE should receive ormonitor a downlink control channel is periodically configured. In otherwords, a description will be made under the assumption that the UEperiodically receives or monitors the downlink control channel and thatthe value of the period is predefined, is configured through ahigher-layer signal, or is indicated through a downlink control channelor a downlink data channel. However, methods proposed in the embodimentsof the disclosure may also be applied to the case where the UEaperiodically receives or monitors the downlink control channel. Forexample, the method proposed in the disclosure may be applied to thecase where the time at which the UE is to receive or monitor a downlinkcontrol channel may be configured or designated in a bit map form. Forexample, the time (symbol or slot) at which the UE is to receive ormonitor the downlink control channel may be configured or designated bythe base station through a bit map defined based on a predetermined timeinterval such as a time of 1 ms or 10 ms.

First Embodiment

The first embodiment describes a method in which a time or periodrequired for a UE to receive a downlink control channel is(re)configured or changed through at least one type of downlink controlinformation transmitted by the base station through a downlink controlchannel.

The UE may receive a configuration for at least one “time or period forreceiving the downlink control channel” from the base station through ahigher-layer signal. For example, the UE may be configured to receivethe downlink control channel according to a first reception time or afirst reception period (e.g. every N symbols, N ≥1). Also, the UE may beconfigured to receive the downlink control channel according to a secondreception time or a second reception period (e.g. every N slots, N≥1) inaddition to the first reception time or the first reception period.Hereinafter, the first reception time and the first reception period arereferred to as a first reception time/period, and the second receptiontime and the second reception period are described as a second receptiontime/period. In this case, the first reception time/period and thesecond reception time/period may be different. Also, it is possible tofurther configure a time or a period for the UE to receive the downlinkcontrol channel, in addition to the first reception time/period and thesecond reception time/period.

Meanwhile, at least one time or period (e.g. one of the first receptiontime/period or the second reception time/period) of the downlink controlchannel reception time or period configured for the UE may be defined inadvance between the base station and the UE, or may be configuredthrough system information (e.g. a master information block (MIB),remaining system information (RMSI), a system information block (SIB),or the like) transmitted by the station. For example, the firstreception time/period may be defined in advance between the base stationand the UE, and the first time or period may be defined differentlyaccording to a frequency band, a bandwidth part, or a subcarrierinterval. In this case, a time and frequency resource domain (searchspace or CORESET) through which a downlink control channel, which the UEis to receive or monitor in the first reception time/period and thesecond reception time/period, can be transmitted may be configureddifferently. Further, the types of downlink control information (DCI)that the UE is to receive or monitor in the first reception time/periodand the second reception time/period may be different.

Assuming that a time or period at which the UE receives a downlinkcontrol channel is configured through a higher-layer signal from thebase station, that is, a first reception time/period is configuredthrough a higher-layer signal, the following description will be made.The content of the disclosure may also be applied even when the firstreception time/period is predefined between the base station and the UEor is configured through system information (e.g. a master informationblock (MIB), remaining system information (RMSI), a system informationblock (SIB)) or the like transmitted by the station. A first receptiontime/period, at which the UE is to receive a downlink control channel,is configured through a higher-layer signal from the base station, andthen the UE receives the downlink control channel according to the firstreception time/period. When the UE determines, through the downlinkcontrol channel reception, that the base station has transmitteddownlink control information (DCI) to the UE, the UE may, according tothe received downlink control information, receive a downlink signal ortransmit an uplink signal.

The following more detailed description will be made with reference toFIG. 5 as an example. FIG. 5 illustrates a downlink control channelreception time or period of a base station and a UE according to thedisclosure.

The UE is configured to receive a downlink control channel in a firstreception time 570 or a first reception period 575 with respect to theunlicensed band cell through a higher-layer signal from the basestation. The UE receives the downlink control channel at the configuredfirst reception time/period and determines whether the base station hastransmitted downlink control information to the UE. The base stationperforms a channel access procedure 520 for an unlicensed band in orderto transmit a downlink signal to the UE through the unlicensed band.When it is determined through the channel access procedure that theunlicensed band is an idle channel, the base station may transmit adownlink control channel or a downlink data channel to the UE after atime 530 at which the unlicensed band has been determined to be an idlechannel.

When a base station wishes to transmit a downlink signal to a UE forwhich a first signal reception time 570 or period 575 has beenconfigured, the base station may transmit a downlink control channel atan earliest time 535 of the first signal reception time 570 or period575 of the UE among times after the time 530 at which the unlicensedband is determined to be an idle channel. At this time, the base stationmay transmit a specific signal (e.g. an occupancy signal) 532 betweenthe time 530 at which the base station has determined that theunlicensed band is the idle channel and the time at which the basestation transmits the downlink control channel or the downlink datachannel. At this time, the UE may not receive the specific signal 532.The UE, for which the first signal reception time 570 or period 575 hasbeen configured as described above, may receive downlink controlinformation (DCI) or uplink/downlink scheduling information, whichconfigures the UE to receive a downlink signal or transmit an uplinksignal, through the downlink control channel transmitted by the basestation at the time 535.

Since the base station and the UE cannot know the result of the channelaccess procedure for the unlicensed band of the base station, “the time530 or symbol at which the base station determines that the unlicensedband is an idle channel”, “the time or symbol at which the base stationcan transmit a downlink control channel or a downlink data channel”, and“the first signal reception time or period configured for the UE towhich downlink control information is to be transmitted” may all bedifferent. In this case, in order to continue to occupy of theunlicensed band, the base station may transmit a specific signal oroccupancy signal between “the time 530 or symbol at which the unlicensedband is determined to be an idle channel” and “the time or symbol atwhich a downlink control channel or a downlink data channel can betransmitted”, or between “the time 530 or symbol at which the unlicensedband is determined to be an idle channel” and “the time or symbol atwhich a downlink control channel or a downlink data channel can betransmitted”, or “the first signal reception time or period configuredfor the UE to which downlink control information is to be transmitted”.

In order to minimize the transmission of the specific signal oroccupancy signal as described above, the base station may configure thefirst signal reception time or period of the UE to be short (e.g. everysymbol) so that the UE frequently receives a downlink control channel.The frequent reception of the downlink control channel, as describedabove, is necessary in order to minimize the transmission of theoccupancy signal before the base station occupies the unlicensed band orduring the channel access procedure. However, the UE does not need tofrequently receive the downlink control channel as described abovewithin the maximum channel occupancy interval after the base stationoccupies the unlicensed band.

Therefore, it is preferable that the UE receives the downlink controlchannel according to a downlink control channel reception time or perioddifferent from the first signal time or period within an interval inwhich the channel is occupied and used after at least the base stationoccupies the unlicensed band. In other words, there is a need for amethod which makes it possible to (re)configure or change the configureddownlink control channel reception time or period of the UE according tothe channel occupation state of the base station or informationcorresponding thereto, thereby minimizing unnecessary downlink controlchannel reception and monitoring.

To this end, when the base station determines that the unlicensed bandis idle after performing the channel access procedure and then occupiesthe channel, the base station may inform UEs of whether the unlicensedband is occupied or information corresponding thereto, so as to allowthe UEs to change the downlink control channel reception time or period.Whether the unlicensed band is occupied or the corresponding informationwill be described in detail below.

In the case of a UE that does not receive downlink control information(DCI) or uplink/downlink scheduling information from the base station(in other words, referred to as a UE for which the base station does notconfigure downlink signal reception or uplink signal transmission duringthe channel occupancy interval), the UE frequently receives a downlinkcontrol channel according to the first signal reception time 570 orperiod 575, and thus may unnecessarily consume power for the downlinkcontrol channel reception. Therefore, the base station may perform thechannel access procedure and may transmit a downlink signal including atleast the downlink control channel in the unlicensed band when theunlicensed band is determined to be an idle channel through the channelaccess procedure.

The downlink signal may be transmitted through a downlink controlchannel transmitted in common to a cell-common or specific UE group (acell-common PDCCH, a UE-group-common PDCCH (GC-PDCCH), or a downlinkcontrol channel which has been scrambled with a predefined orpreconfigured RNTI and is thus distinguishable, hereinafter, referred toas a common PDCCH or a C-PDCCH). Accordingly, the base station maytransmit the result of the channel access procedure performed by thebase station, information corresponding thereto, or information on aslot format to both a UE having received downlink or uplink schedulingfrom the base station and a UE which has not received downlink or uplinkscheduling from the base station. At this time, the base station maytransmit, to the UEs, the result of the channel access procedureperformed by the base station, information corresponding thereto, orinformation on a slot format through UE-specific downlink controlinformation (UE-specific DCI) (or a downlink control channel scrambledwith a UE-specific identifier (C-RNTI)).

Here, the result of the channel access procedure or information theretoor information on a slot format may include at least one among thelength of a channel occupancy interval, information on a downlink and/oruplink transmission interval (e.g. the downlink and/or uplinktransmission start time (or offset) and a transmission interval length),or slot format indicator (SFI) information for one or more slots. Evenwhen the information does not include information on a downlink and/oruplink transmission interval or slot format indicator (SFI) information,the UE, having determined that the C-PDCCH has been correctly received,may determine according to the result of the C-PDCCH reception that thebase station has occupied the unlicensed band.

When the UE receives the C-PDCCH including at least one of theinformation on a downlink and/or uplink transmission interval or theslot format indicator (SFI) information as described above, the UE maydetermine a channel occupancy interval of the base station through theinformation and may receive a downlink control channel according to asecond signal reception time 580 or period 585 in the determined channeloccupancy interval. In other words, 1) the UE may receive a downlinkcontrol channel according to the configured first signal reception time570 or period 575, 2) when a received C-PDCCH includes at least one ofthe information on a downlink and/or uplink transmission interval or theslot format indicator (SFI) information, the UE may change a downlinkcontrol channel reception time or period to the second signal receptiontime 580 or a period 585 in the channel occupancy interval determinedthrough the C-PDCCH to receive a downlink control channel, and 3) afterthe determined channel occupancy interval, the UE may again receive adownlink control channel according to a first signal reception time 590or period 595.

In this case, the second signal reception time 580 or period 585 may bepredefined as a value different from the first signal reception time 570or period 575 between the base station and the UE, may be configured forthe UE by the base station through a higher-layer signal, or may beindicated to the UE, through the C-PDCCH, by a second signal receptiontime 580 or period 585 value or an offset value from the first signalreception time 570 or period 575. At this time, multiple second signalreception times 580 or periods 585 may be predefined between the basestation and the UE, or multiple second signal reception times 580 orperiods 585 may be configured for the UE through a higher-layer signalfrom the base station.

Alternatively, the base station may select one of the multiple secondsignal reception times 580 or periods 585 predefined or configured forthe UE through a higher-layer signal, and may indicate the selectedsecond signal reception time 580 or period 585 to the UE through aC-PDCCH. For example, the base station may configure four differentsecond signal reception times 580 or periods 585 to the UE through ahigher-layer signal, may select one of the four values, and may transmitthe same via a C-PDCCH, thereby indicating the second signal receptiontime 580 or period 585 of the UE. At this time, the first signalreception time 570 or period 575 may be included in the multiple secondsignal reception times 580 or periods 585. The second signal receptiontime 580 or period 585 for a C-PDCCH and the second signal receptiontime 580 or period 585 for UE-specific downlink control information maybe configured to be identical to or different from each other.

For example, a base station may include, in a C-PDCCH, information on atime or slot that the base station desires to use for downlink signaltransmission or uplink signal transmission of a UE with respect to anunlicensed band determined to be idle after a channel access procedure,and may transmit the same to the UE. The information on the time or slotmay be within a maximum channel occupancy interval. For example, in thecase of Japan having a maximum channel occupancy interval of 4 ms, abase station may include, in a C-PDCCH, information on anuplink/downlink transmission interval that the base station wishes touse within the 4 ms interval with respect to an unlicensed banddetermined to be idle after a channel access procedure (e.g. downlinktransmission is performed for the first 2 ms and uplink transmission isconfigured for 2 ms thereafter), and may transmit the same to a UE.

In order to notify the UE of the downlink transmission interval and theuplink transmission interval, the base station may include at least onevalue among a downlink transmission interval offset, a downlinktransmission interval length, an uplink transmission interval offset,and an uplink transmission interval length in a C-PDCCH, and maytransmit the same to the UE. At this time, the downlink transmissioninterval offset is a value indicating a start time (a symbol or slot) atwhich the downlink transmission interval begins with reference to “theindex of a symbol or slot in which the C-PDCCH has been received” or“the index of a slot immediately following the slot in which the C-PDCCHhas been received”, and may include a symbol or a slot. The uplinktransmission interval offset is a value indicating a start time (asymbol or slot) at which the uplink transmission interval begins withreference to “a symbol or slot in which the C-PDCCH has been received”,or indicating a start time (a symbol or slot) at which the uplinktransmission interval begins with reference to “the end time (symbol orslot) of the downlink transmission interval”. When the uplinktransmission interval offset indicates the start time of the uplinktransmission interval with reference to the end time of the downlinktransmission interval, uplink transmission interval offset informationmay not be included in the C-PDCCH.

As another example, the base station may include, in a C-PDCCH, a slotformat indicator (SFI) for some slots or all transmission slots in themaximum channel occupancy interval to the UE, and may transmit the sameto the UE. The SFI may be within a maximum channel occupancy interval ofthe unlicensed band. For example, when one slot includes K symbols, theSFI is information indicating the number of symbols used for downlink oruplink signal transmission among the K symbols. In other words, throughthe slot format indicator, the UE may determine that all of the Ksymbols are used for downlink transmission, all of the K symbols areused for uplink transmission, or some K1 of the K symbols are used fordownlink transmission, and all of the remaining symbols or some K2 ofthe remaining symbols are used for uplink transmission. In this case,some of the K symbols may not be used for both downlink and uplinktransmission, or may be used as a gap necessary for switching fromdownlink to uplink (i.e., K≥K1+K2).

Further, the SFI information includes information indicating that all ofthe K symbols in the slot are unknown symbols, which are not usedneither for downlink signal transmission nor for uplink signaltransmission, or flexible symbols that can be changed to downlink oruplink according to scheduling information. In the unknown or flexiblesymbols or slots, the UE may not perform downlink signal reception oruplink signal transmission, or may perform downlink signal reception oruplink signal transmission according to information scheduled throughUE-specific DCI in addition to the C-PDCCH. The UE may receive thedownlink control channel using the first reception time/period in theunknown slot. At this time, the UE may not perform a downlink controlchannel reception operation in the symbol or slot designated to be anuplink transmission symbol through the slot format indicator.

In this case, in order to transmit the slot format indicator informationof some or all of the transmission slots in the maximum channeloccupancy interval, slot format indicator information of a slotcorresponding to the number of slots included in the maximum channeloccupancy interval or corresponding to a number obtained by subtractingone from the number of slots may be included in a C-PDCCH andtransmitted to the UE. For example, when the maximum channel occupancyinterval of X ms includes a total of Y slots, slot format indicatorinformation of each of the Y slots may be sequentially included in theC-PDCCH.

At this time, at least one of the Y pieces of slot format informationmay not be actually used or may be indicated as being in the unknownstate. For example, as shown in FIG. 5, when up to five slots areincluded in the maximum channel occupancy interval 510, the C-PDCCH 535,which the base station has transmitted after determining that theunlicensed band is idle, may sequentially include slot format indicatorinformation of five slots (N−1, N, N+1, N+2, N+3), including slot formatindicator information of slot N−1, in which the C-PDCCH 535 istransmitted.

When the C-PDCCH is transmitted at any time point in slot N−1 (when theC-PDCCH is transmitted at a time point after the first symbol of slotN−1 or is transmitted after an initial time and frequency resourcedomain (or CORESET) in which the C-PDCCH can be transmitted within slotN−1), the base station may transmit the C-PDCCH 535 including onlyformat information of the remaining slots excluding format indicatorinformation of slot N−1 in which the C-PDCCH is transmitted (e.g. slotformat information of slots N, N+1, N+2, and N+3). At this time, asdescribed above, the UE having received the C-PDCCH 535 in apredetermined symbol of slot N−1 may determine that the slot formatindicator information included in the C-PDCCH includes slot formatindicator information of the slot immediately following the slot inwhich the C-PDCCH was received. Here, the predetermined symbol is thesymbol after the first symbol in slot N−1. In another example, whenconsidering the minimum processing time (X) necessary for decoding theC-PDCCH received in slot N−1 by the UE and acquiring slot formatindicator information from the decoded signal, the predetermined symbolis the symbol before an X symbol with reference to a slot N start symbolin consideration of the downlink control signal processing minimum timeof the UE.

When the base station transmits the C-PDCCH 535 including the formatinformation of the remaining slots excluding the format indicatorinformation for slot N−1, in which the C-PDCCH is transmitted, the UEmay assume that slot N−1, in which the C-PDCCH 535 is received, isentirely used as a downlink transmission symbol. Alternatively, the UEmay determine that slot N−1, in which the C-PDCCH 535 is received, is anunknown or flexible symbol, or may perform a signaltransmission/reception operation in the slot according to downlink oruplink scheduling information. At this time, the scheduling informationmay include at least one of scheduling information received beforereception of the C-PDCCH 535 or scheduling information received in slotN−1.

In order to notify the UE of the position of the slot to which the slotformat indicator information is applied or begins to be applied, theC-PDCCH may include an offset for the slot format indicator informationincluded in the C-PDCCH (i.e. time information to which the slot formatindicator information included in the C-PDCCH is applied). The slotformat indicator information offset may be applied with reference to aC-PDCCH reception slot. In FIG. 5, for example, slot N−1 may be used asa reference. At this time, the slot format indicator information offsetmay be applied with reference to the slot immediately following theC-PDCCH reception slot. In the case of FIG. 5, for example, slot N canbe applied as a reference. Alternatively, when the UE receives a C-PDCCHin a symbol after the first symbol of a particular slot, the slot formatindicator information offset may be applied with reference to the slotimmediately following the slot in which the C-PDCCH is received. Asanother example, the minimum processing time (X) required to decode theC-PDCCH received by the UE and obtain the slot format indicatorinformation from the decoded signal may be considered. When a symbol inwhich the UE receives the C-PDCCH is a symbol before a 14-X symbol ofthe particular slot, the slot format indicator information offset isapplied based on the slot immediately following the C-PDCCH receptionslot. When a symbol in which the UE receives the C-PDCCH is a symbolafter the 14-X symbol, the slot format indicator information offset maybe applied with reference to a symbol after two slots from the symbol inwhich the C-PDCCH is received.

Consideration will be given to the case where a C-PDCCH, which the basestation in FIG. 5 transmits after the unlicensed band is determined tobe idle through the channel access procedure, includes at least one ofthe downlink and/or uplink transmission interval information or the slotformat indicator (SFI) information as described above. As describedabove, upon receiving the C-PDCCH including at least one of the downlinkand/or uplink transmission interval information or the slot formatindicator (SFI) information, the UE may receive a downlink controlchannel according to the configured second signal reception time 580 orperiod 585. In other words, 1) the UE may continue to receive a downlinkcontrol channel according to the configured first signal reception time570 or period 575, and 2) when the received C-PDCCH includes at leastone of the downlink and/or uplink transmission interval information orthe slot format indicator (SFI) information, the UE may change adownlink control channel reception time or period to the second signalreception time 580 or period 585 so as to receive a downlink controlchannel.

A description will be made with reference to FIG. 5 below. The UEreceiving a downlink control channel according to the first signalreception time 570 or period 575 receives the C-PDCCH 535. When thereceived C-PDCCH 535 includes information on a downlink transmissioninterval (e.g. when information included in the C-PDCCH indicates atleast one among a downlink transmission slot start slot (or offset), thenumber of downlink transmission slots, and the number of downlinksymbols of the downlink transmission slots (for example, in FIG. 5, wheninformation included in the C-PDCCH indicates that slot N to slot N+3are downlink transmission slots, slot N+3 is a downlink transmissionslot including 12 downlink transmission symbols)), the UE receives adownlink control channel according to the second signal reception time580 or period 585 during the downlink transmission interval indicated bythe C-PDCCH 535. After the downlink transmission interval indicated bythe C-PDCCH 535, the UE may receive a downlink control channel accordingto the first signal reception time 570 or period 575.

At this time, the downlink transmission slot start slot (or offset)refers to a slot through which the C-PDCCH is transmitted, or a slotfollowing the slot through which the C-PDCCH is transmitted. When thedownlink transmission slot start slot (or offset) refers to a slotthrough which the C-PDCCH is transmitted, or a slot following the slotthrough which the C-PDCCH is transmitted, the C-PDCCH may not includedownlink transmission start slot (or offset) information. In this case,when the C-PDCCH is transmitted in a symbol subsequent to the firstsymbol among symbols in a transmission slot, the downlink transmissionstart slot (or offset) refers to a slot following a slot through whichthe C-PDCCH is transmitted. When the C-PDCCH is transmitted in the firstsymbol among the symbols in the transmission slot, the downlinktransmission start slot (or offset) refers to a slot through which theC-PDCCH is transmitted.

Also, when the C-PDCCH is transmitted in a symbol after the first symbolamong the symbols in the transmission slot, information on the slotthrough which the C-PDCCH is transmitted may not be included in thedownlink transmission interval information indicated in the C-PDCCH.When the information on the slot through which the C-PDCCH istransmitted is not included in the downlink transmission intervalinformation indicated by the C-PDCCH, the UE may determine that allsymbols of the slot through which the C-PDCCH is transmitted are usedfor downlink signal transmission. Alternatively, when the information ofthe slot through which the C-PDCCH is transmitted is not included in thedownlink transmission interval information indicated by the C-PDCCH, theUE may determine that all symbols of the slot through which the C-PDCCHis transmitted are unknown or flexible symbols, and may perform,according to downlink or uplink scheduling information, signaltransmission/reception in a slot in which the C-PDCCH is transmitted.

When the UE receives a C-PDCCH in a time or slot after the time or slotN−1 at which the C-PDCCH 535 is received, the UE may determine adownlink control channel reception time or period according toinformation included in a most recently received C-PDCCH in the channeloccupancy interval (e.g. information on the downlink and/or uplinktransmission interval, the slot format indicator (SFI) information, andthe like).

The case in which the C-PDCCH includes slot format indicator informationof one or more slots is will be described as an example. When thechannel occupancy interval 510 includes N slots, for example, when slotsN−1, N, N+1, N+2, and N+3 are allocated to the channel occupancyinterval 510 in FIG. 5, slot format indicator information of N slots maybe sequentially included in the C-PDCCH. For example, from the mostsignificant bit (MSB) of the field for transmitting the slot formatindicator information in the C-PDCCH, the slot format indicatorinformation of N slots including a start slot in which the base stationstarts occupying a channel can be sequentially mapped. At this time,assuming that the slot format indicator information includes L bits, thesize of a field for transmitting the slot format indicator informationis L*N bits. In FIG. 5, the base station may transmit slot indicatorinformation for each slot from slot N−1 to slot N+3 through the C-PDCCH532.

When the base station transmits a C-PDCCH 550 in slot N, since the slotformat indicator information may include only slot indicator informationfor slots from slot N to slot N+3, the size of a field for transmittingthe slot format indicator information may be reduced. However, when thesize of the field for transmitting the slot format indicator informationchanges according to the C-PDCCH transmission slot, the size of theC-PDCCH changes, and thus the C-PDCCH reception and detection complexityof the UE increases. Therefore, it is preferable that the size of thefield for transmitting the slot format indicator information be keptconstant regardless of the C-PDCCH transmission slot.

Therefore, when the base station transmits the C-PDCCH 550 in slot N,slot format indicator information of slots from slot N to slot N+3 issequentially mapped to the most significant bit of the field fortransmitting the slot format indicator information, and slot formatindicator information, predefined for a slot (e.g. slot N−1) previouslyused in the channel occupancy interval or having no valid slot formatindicator information, may be mapped to a least significant bit (LSB) ofthe field. For example, a slot format indicator of one slot (e.g. slotN−1) is represented as slot format indicator information indicating“unknown” and mapped to a least significant bit of a field fortransmitting the slot format indicator information of the C-PDCCH 550.

Similarly, when the base station transmits a C-PDCCH 552 in slot N+1,slot format indicator information of slots from slot N+1 to slot N+3 issequentially mapped to the most significant bit of the field fortransmitting the slot format indicator information, and slot formatindicator information, predefined for a slot (e.g. slots N−1 and N)previously used in the channel occupancy interval or having no validslot format indicator information, may be mapped to a least significantbit (LSB) of the field. For example, slot format indicator informationindicating that the two slots are unknown may be included in the leastsignificant bit of the field for transmitting the slot format indicatorinformation.

In other words, the slot format indicator information transmittedthrough a C-PDCCH includes slot format indicator information of a slotin which the C-PDCCH is transmitted and a valid slot after the slot inwhich the C-PDCCH is transmitted in a channel occupancy interval of thebase station, and may include a predefined slot format indicator for analready indicated slot or an already occupied or used slot in thechannel occupancy interval. Accordingly, the UE can use only the slotformat indicator information of the slot in which the C-PDCCH istransmitted and a valid slot thereafter.

Alternatively, the base station may transmit, through a C-PDCCH, slotindicator information for each slot from slot N−1 to slot N+3, whereinthe slot indicator information is sequentially included according to theslot in a slot indicator information field in the C-PDCCH from the MSBof the field. At this time, the base station may indicate valid slotindicator information among the slot format indicators to the UE throughan additional indicator of the slot indicator information of the slotformat indicator. For example, the base station may sequentiallyinclude, in the C-PDCCH 535, slot format indicator information of eachslot from slot N−1 to slot N+3 and transmit the same through the C-PDCCH535 in slot N−1. Through a field indicating a valid slot formatindicator among the slot format indicators, the base station mayindicate that the slot format indicators are valid from the slot N−1.When the C-PDCCH 550 is transmitted in slot N, the base station maysequentially include, in the C-PDCCH 550, slot format indicatorinformation of each slot from slot N−1 to slot N+3 and transmit thesame. Further, the base station may indicate that the slot formatindicators are valid from slot N through a field indicating a valid slotformat indicator among the slot format indicators.

When the C-PDCCH 552 is transmitted in slot N+1, the base station maysequentially include, in the C-PDCCH 552, slot format indicatorinformation of each slot from slot N−1 to slot N+3 and transmit thesame. Further, the base station may indicate that the slot formatindicators are valid from slot N+1 through a field indicating a validslot format indicator among the slot format indicators. Slots N−1 and Nbefore the valid slot N+1 indicated by the valid slot format indicatormay be indicated as predefined slot format indicator information (e.g.slot format indicator information indicating “unknown” or slot formatindicator information in which all symbols in a slot are uplinktransmission symbols, or the like). At this time, the UE may ignore slotformat indicator information of slots N−1 and N before the valid slotN+1 indicated by the valid slot format indicator. In addition, the fieldindicating the effective slot format indicator should be able toindicate the number of slots through which the valid slot formatindicator is transmitted in the C-PDCCH. For example, when the C-PDCCH552 is transmitted, a field indicating a valid slot format indicator mayindicate the value 3.

Another example will be described with reference to FIG. 5 below.Consideration will be given to the case where a UE receiving a downlinkcontrol channel according to the first signal reception time 570 orperiod 575 receives the C-PDCCH 535 and the received C-PDCCH 535includes at least one of downlink transmission interval information oruplink transmission interval information (e.g. the case including atleast one slot format indicator (SFI) information for at least one slotor a start slot (or offset) to which the slot format indicator isapplied). The UE may receive a downlink control channel according to thesecond signal reception time 580 or period 585 in slots having slotformats indicated through slot format indicator information indicated inthe C-PDCCH 535. Further, the UE may receive a downlink control channelaccording to the first signal reception time 570 or period 575 in a slothaving a slot format which is not indicated through slot formatindicator information indicated in the C-PDCCH 535, some slots of slotshaving slot formats which have been indicated in the C-PDCCH 535 (e.g.the last slot among the slots having the indicated slot formats or aslot having an indicated specific slot format), or a slot after the slothaving the indicated slot format.

Here, the slot having the indicated specific slot format includes apredefined slot format, for example, a slot format indicating that allsymbols of a slot are in a flexible state or an unknown state in whichnone of the symbols of the slot are used for downlink signaltransmission or for uplink signal transmission. Meanwhile, a start slot(or offset) to which a slot format indicator is applied is a slotthrough which the C-PDCCH is transmitted or a slot following the slotthrough which the C-PDCCH is transmitted. When the start slot refers toa slot through which the C-PDCCH is transmitted or a slot following theslot through which the C-PDCCH is transmitted, the C-PDCCH may notinclude information on the start slot (or offset) to which the slotformat indicator is applied. In this case, when the C-PDCCH istransmitted in a symbol after the first symbol among symbols in atransmission slot, the start slot (or offset), to which the slot formatindicator is applied, may be determined to refer to a slot following aslot in which the C-PDCCH is transmitted. Further, it is determined thatwhen the C-PDCCH s transmitted in the first symbol among the symbols inthe transmission slot, the start slot (or offset), to which the slotformat indicator is applied, may be determined to refer to a slotthrough which the C-PDCCH is transmitted.

Also, when the C-PDCCH is transmitted in a symbol after the first symbolamong symbols in a transmission slot, the slot format indicatorinformation indicated in the C-PDCCH may not include information on aslot through which the C-PDCCH is transmitted. When the slot formatindicator information indicated in the C-PDCCH does not include theinformation on the slot through which the C-PDCCH is transmitted, the UEmay determine that all symbols of the slot in which the C-PDCCH istransmitted are used for downlink signal transmission or are unknown.Further, when it is indicated that a slot corresponding to a slot formatindicator indicated in the C-PDCCH does not include a downlinktransmission interval or symbol, the UE may not receive a downlinkcontrol channel in the slot, or may receive a downlink control channelaccording to the first signal reception time 570 or period 575.

When the UE again receives a C-PDCCH at a time or slot after the time orslot N−1 at which the C-PDCCH 535 has been transmitted, the UE maydetermine a downlink control channel reception time or period accordingto information included in the most recently received C-PDCCH. At thistime, the types of information on downlink transmission intervalsincluded in C-PDCCHs transmitted at different times or symbols may bedifferent from each other.

In this case, the second signal reception time 580 or period 585 may bepredefined as a value different from the first signal reception time 570or period 575 between the base station and the UE, may be configured inthe UE through a higher-layer signal from the base station, or may beindicated by a second signal reception time 580 or period 585 value oran offset value from the first signal reception time 570 or period 575to the UE through the C-PDCCH. At this time, multiple second signalreception times 580 or periods 585 may be predefined between the basestation and the UE, or may be configured in the UE through ahigher-layer signal from the base station. The base station may selectone of the multiple second signal reception times 580 or periods 585predefined or configured in the UE through the higher-layer signal, andmay indicate the selected second signal reception time 580 or cycle 585to the UE through a C-PDCCH. For example, the base station may configurefour different second signal reception times 580 or periods 585 to theUE through a higher-layer signal, and may select one of the four valuesto indicate the selected one value via a C-PDCCH. At this time, themultiple second signal reception time 580 or period 585 may include thefirst signal reception time 570 or period 575.

Meanwhile, embodiments of the disclosure includes: the base stationoperation for configuring the first signal reception time/period and thesecond signal reception time/period and indicating the configured timeor period and the UE operation for applying the same, described in theabove embodiment; and the transmission method for an uplink or downlinktransmission interval length or at least one piece of slot formatindicator information transmitted in the C-PDCCH or second C-PDCCH andthe UE operation therefor. The contents described in embodiments of thedisclosure are not limited to a specific embodiment, and may be appliedto all of the embodiments of the disclosure. Therefore, unnecessaryrepetition of a description will be omitted by omitting a description ofparts of the first embodiment that can be applied and determined usingthe contents described in the second, third, and fourth embodiments.

Second Embodiment

The second embodiment relates to a method in which a UE receives adownlink control channel commonly transmitted to a cell-common orspecific UE group (a cell-common PDCCH, a UE-group-common PDCCH(GC-PDCCH), or a downlink control channel which has been scrambled witha predefined or preconfigured RNTI and is thus distinguishable,hereinafter, referred to as a common PDCCH or a C-PDCCH) according to adownlink control channel reception time or period (hereinafter, referredto as a first reception time/period) predefined or configured through ahigher-layer signal from a base station, and the UE, which hasdetermined that a C-PDCCH has been correctly received, receivesUE-specific downlink control information (a UE-specific DPI) (or adownlink control channel scrambled with a UE-specific indicator(C-RNTI)) according to a downlink control channel reception time orperiod (hereinafter, referred to as a second reception time/period)predefined or configured through a higher-layer signal from a basestation.

At this time, when a value or information related to the secondreception time/period is included in the C-PDCCH, the second receptiontime/period may follow the value included in the C-PDCCH. Further, astarting point or offset of the second reception time/period may beapplied with reference to “a symbol or a slot in which the C-PDCCH hasbeen received” or “a symbol or slot after a T symbol or T slot in thesymbol or slot in which the C-PDCCH has been received”. In this case, Tmay be predefined as a value including 0, may be configured through ahigher-layer signal from the base station, or may be included in theC-PDCCH.

Also, the second reception time/period is valid at least within achannel occupancy interval of the base station, and information on theeffective channel occupancy interval may be directly transmitted to theUE through the C-PDCCH, or may be determined through uplink or downlinktransmission interval information include in the C-PDCCH. For example,the UE may determine the channel occupancy interval information of thebase station through an uplink or downlink transmission interval lengthor at least one slot format indicator transmitted in the C-PDCCH.Thereafter, the UE may receive UE-specific downlink control informationaccording to the second reception time/period within the determinedchannel occupancy interval, and may receive at least C-PDCCH accordingto the first reception time/period outside the determined channeloccupancy interval.

In this case, the UE receiving the C-PDCCH according to the firstreception time/period may not receive the UE-specific downlink controlinformation when the C-PDCCH is not received from the base station oroutside the determined channel occupancy interval. That is, the UE mayreceive the UE-specific downlink control information within the channeloccupancy interval determined from a symbol or a slot following thesymbol or the slot in which the C-PDCCH transmitted by the base stationwas correctly received, thereby minimizing the consumption of power bythe UE in receiving and monitoring the downlink control information. Inthis instance, the UE may receive UE-specific downlink controlinformation, starting from the symbol or slot in which the C-PDCCHtransmitted by the base station was correctly received.

Meanwhile, embodiments of the disclosure includes: the base stationoperation for configuring the first signal reception time/period and thesecond signal reception time/period and indicating the configured timeor period, and the UE operation for applying the same, described in theabove embodiments; and a transmission method for an uplink or downlinktransmission interval length or at least one piece of slot formatindicator information transmitted in the C-PDCCH or second C-PDCCH, anda UE operation therefor. The content described in connection with theembodiments of the disclosure is not limited to a specific embodiment,and may be applied to all of the embodiments of the disclosure.Therefore, unnecessary repetition of a description will be omitted byomitting a description of parts of the second embodiment that can beapplied and determined using the content described in the first, third,and fourth embodiments.

Third Embodiment

The third embodiment relates to a method in which a UE activates ordeactivates a second downlink control channel reception time or periodof the UE according to the reception of specific downlink controlinformation or the reception of specific MAC CE information so as to(re)configure or change a downlink control channel time or period. Here,the specific downlink control information may be transmitted through adownlink control channel commonly transmitted to a cell common orspecific UE group (a cell-common PDCCH, a UE-group-common PDCCH(GC-PDCCH), or a downlink control channel which has been scrambled witha predefined or preconfigured RNTI and is thus distinguishable,hereinafter, referred to as a common PDCCH or a second C-PDCCH), or maybe transmitted through UE-specific downlink control information (aUE-specific DPI) (or a downlink control channel scrambled with aUE-specific indicator (C-RNTI)). The C-PDCCH (or the second C-PDCCH)described in the present embodiment may be a C-PDCCH described in thefirst embodiment or the second embodiment, and may be a C-PDCCHtransmitted after being scrambled with an identifier (RNTI) differentfrom UE-specific downlink control information, for example, anidentifier (RNTI) configured through a higher-layer signal from the basestation or predefined in order to activate or deactivate a downlinkcontrol channel reception time or period of the UE.

A more detailed description will be made with reference to FIG. 6 below.FIG. 6 illustrates another example of a downlink control channelreception time or period of a base station and a UE according to thedisclosure.

At least one downlink control channel reception time or period of the UEmay be configured by the base station through a higher-layer signal. Forexample, the UE may be configured to receive a downlink control channelaccording to a first reception time 670 or a first reception period 675(e.g. every N symbols, N≥1, hereinafter, referred to as a firstreception time/period). Further, the UE may be configured to receive adownlink control channel according to a second reception time 680 or asecond reception period 685 (e.g. every N symbols, N≥1, hereinafter,referred to as a second reception time/period) in addition to the firstreception time/period.

The UEs receive the downlink control channel according to the configuredfirst signal reception time/period. When the UE receives a secondC-PDCCH transmitted by the base station in slot N and the receivedsecond C-PDCCH includes information indicating the activation of thesecond reception time/period (e.g. when the UE determines that theactivation of the second reception time/period is indicated through avalue of a bit string indicating the activation of the second receptiontime/period to the second C-PDCCH, or when specific bits among bitstrings included in the second C-PDCCH are indicated by previouslydefined or promised bits), the UE may determine that the received secondC-PDCCH indicates the activation of the second reception time/period,and may receive a downlink control channel according to the secondreception time 580 or period 585.

In this case, the UE may receive the downlink control channel accordingto the second reception time 580 or period 585 until the second C-PDCCHindicates deactivation or release of the second reception time/period.When the second C-PDCCH indicates deactivation or release of the secondreception time/period, the UE may immediately receive the downlinkcontrol channel according to the first reception time/period. At thistime, the first reception time/period may be applied from a T symbol orT slot after reception of the second C-PDCCH indicating the deactivationor release of the second reception time/period. In this case, T may bepredefined as a value including 0, may be configured through ahigher-layer signal from a base station, or may be included in thesecond C-PDCCH.

At this time, the second reception time/period may be deactivated orcanceled through a deactivation timer, in addition to a method in whichthe second C-PDCCH indicates the deactivation or release of the secondreception time/period. For example, the UE determines that the secondC-PDCCH activates the deactivation timer from the time point at whichthe second reception time/period is activated and that the secondreception time/period has been deactivated or released after aconfigured or defined timer time, and receive a downlink control channelaccording to the first reception time/period.

In this case, the second signal reception time 680 or period 685 may bepredefined as a value different from the first signal reception time 670or period 675 between the base station and the UE, may be configured forthe UE by the base station, may be indicated to the UE by a secondsignal reception time 680 or period 685 value or an offset value fromthe first signal reception time 670 or period 675 through the C-PDCCH,or may be indicated to the UE by a second signal reception time 680 orperiod 685 value or an offset value from the first signal reception time670 or period 675 through the second C-PDCCH.

At this time, multiple second signal reception times 680 or periods 685may be predefined between the base station and the UE, or the multiplesecond signal reception times 680 or periods 685 may be configured forthe UE through a higher-layer signal from the base station. The basestation may select one of the multiple second signal reception times 680or periods 685 predefined or configured for the UE through thehigher-layer signal, and may indicate the selected one to the UE througha C-PDCCH or a second C-PDCCH. For example, the base station mayconfigure four different second signal reception times 680 or periods685 to the UE via a higher-layer signal, may select one of the fourvalues, and may indicate the second signal reception time 680 or period685 of the UE through the C-PDCCH or the second C-PDCCH. At this time,the first signal reception time 670 or period 675 may be included in themultiple second signal reception times 680 or periods 685.

Meanwhile, embodiments of the disclosure includes: the base stationoperation for configuring the first signal reception time/period and thesecond signal reception time/period and indicating the configured timeor period, and the UE operation for applying the same, described in theabove embodiments; and the transmission method for an uplink or downlinktransmission interval length or at least one piece of slot formatindicator information transmitted in the C-PDCCH or second C-PDCCH andthe UE operation therefor. The content described in connection withembodiments of the disclosure is not limited to a specific embodiment,and may be applied to all of the embodiments of the disclosure.Therefore, unnecessary repetition of a description will be omitted byomitting a description of parts of the third embodiment that can beapplied and determined using the content described in the first, second,and fourth embodiments.

Fourth Embodiment

The fourth embodiment relates to a method in which one or more bandwidthparts are configured for a UE and when a downlink control channelreception time or period are configured in each bandwidth part, the UEdetermines the downlink control channel reception time or period to bereceived by the UE.

FIG. 7 illustrates another example of a downlink control channelreception time or period of a base station and a UE of the disclosure.

According to FIG. 7, for example, when a downlink control channelreception frequency band in a first signal reception time 770 or period775 is referred to as a first bandwidth part (or a bandwidth part 760)and a downlink control channel reception frequency band in a secondsignal reception time 780 or period 785 is referred to as a secondbandwidth part 765, the first bandwidth part and the second bandwidthpart may be different from each other. At this time, the downlinkcontrol channel reception frequency band in the first signal receptiontime 770 or period 775 is different from the downlink control channelreception frequency band in the second signal reception time 780 orperiod 785. For example, the second bandwidth part 765 may be themaximum frequency band that the UE can support, or a frequency band thatis predefined or configured through a higher-layer signal. The firstbandwidth part 760 may be a minimum frequency band of the UE, afrequency band necessary for receiving a synchronization signal or abroadcast channel, or a frequency band predefined or configured througha higher-layer signal. In other words, the second bandwidth part 765 maybe a frequency band that is larger than the first bandwidth part 760 andincludes the first bandwidth part 760.

In general, when a UE receives a downlink signal by using a relativelysmall frequency band, the UE can reduce power consumption, compared towhen the UE receives a downlink signal by using a relatively largefrequency band. Accordingly, in order to reduce the power consumption ofa general UE, it is effective for the UE to receive or monitor adownlink control channel by using a narrow frequency band (e.g. thefirst bandwidth part 760) and to receive a downlink data channel byusing a broad frequency band (e.g. the second bandwidth part 765) whenhigh-volume downlink data is required to be transmitted. However, thesecond bandwidth part 765 may be equal to or smaller than the firstbandwidth part 760. Further, the content of the disclosure may beapplied even when the first bandwidth part 760 and the second bandwidthpart 765 partially overlap each other or are spaced apart from eachother without overlapping each other.

When the downlink control channel reception time or period is configureddifferently according to the frequency band or the bandwidth part asdescribed above, in at least one bandwidth part, the UE receives ormonitors a downlink control signal according to a downlink controlsignal reception interval or period configured in the bandwidth part.Further, in a downlink control signal reception interval or periodconfigured in a bandwidth part other than the bandwidth part, the UE maynot receive a downlink control channel in the bandwidth part until thebandwidth part other than the bandwidth part is used or activated.

For example, in FIG. 7, a UE may receive a configuration (e.g.,frequency domain information for each bandwidth part) relating to thefirst bandwidth part 760 and the second bandwidth part 765 from the basestation through a higher-layer signal. Further, a downlink controlchannel reception time or period for each bandwidth part may also beconfigured through a higher-layer signal from the base station. In otherwords, the UE may receive: a configuration relating to the firstbandwidth part 760, a configuration relating to the downlink controlchannel reception time 770 or period 775 for the first bandwidth part760, and configuration information relating to a resource in which adownlink control channel is to be received; and a configuration for thesecond bandwidth part 765, a configuration relating to the downlinkcontrol channel reception time 780 or period 785 and the downlinkcontrol channel for the second bandwidth part 765, and configurationinformation relating to a resource in which a downlink control channelis to be received.

In this case, when the first bandwidth part 760 is previously defined orconfigured as a basic operation frequency band of the UE, the UEreceives a downlink control channel according to the downlink controlchannel reception time 770 or period 775 for the first bandwidth part760 until a separate instruction or signal is detected. At this time,the UE may not receive a downlink control channel in the downlinkcontrol channel reception time 780 or period 785 for the secondbandwidth part 765. In this case, the UE may directly receive, through ahigher-layer signal, a basic bandwidth part for the downlink controlchannel reception of the UE among the configured first bandwidth part760 or the configured second bandwidth part 765. Alternatively, the UEmay determine that a bandwidth part having an index in which thebandwidth part index representing the bandwidth part is the lowest isthe basic bandwidth part of the UE. Further, in the above description,it is assumed that the UE has received a configuration for two bandwidthparts. However, the content of the disclosure may be applied even whenthe UE has received a configuration for two or more bandwidth parts.

Consideration will be given to the case in which the UE receives whetherthe UE has occupied the unlicensed band or information correspondingthereto (e.g. at least one of uplink or downlink transmission intervallength or at least one piece of slot format indicator information) fromthe base station through the C-PDCCH, the second C-PDCCH, theUE-specific downlink control information, etc. proposed in the aboveembodiments, or to the case in which the UE receives an indicatorindicating a change of a bandwidth part of the UE from the firstbandwidth part 760 to the second bandwidth part 765 through a C-PDCCH, asecond C-PDCCH, a UE-specific downlink control information, or ahigher-layer signal including a MAC CE. The UE may receive a downlinkcontrol channel in the downlink control channel reception time 780 orperiod 785 for the second bandwidth part 765. At this time, while the UEreceives the downlink control channel in the downlink control channelreception time 780 or period 785 for the second bandwidth part 765, theUE may not receive the downlink control channel in the downlink controlchannel reception time 770 or period 775 for the first bandwidth part760.

Then, consideration will be given to the case in which the UE receivesan indicator indicating a change of the bandwidth part of the UE fromthe second bandwidth part 765 to the first bandwidth part 760 from thebase station through the C-PDCCH, the second C-PDCCH, the UE-specificdownlink control information, or a higher-layer signal including MAC CE,etc. proposed in the above embodiments, or the case in which apredefined time passes after the bandwidth part of the UE is changedfrom a first bandwidth part 560 to a second bandwidth part 565. At thistime, the UE receives a downlink control channel at the downlink controlchannel reception time 770 or period 775 for the first bandwidth part760, and may not receive the downlink control channel at the downlinkcontrol channel reception time 780 or period 785 for the secondbandwidth part 765.

Various embodiments of the disclosure includes: the base stationoperation for configuring the first signal reception time/period and thesecond signal reception time/period and indicating the configured timeor period, and the UE operation for applying the same, described in theabove embodiments; and a transmission method for an uplink or downlinktransmission interval length or at least one piece of slot formatindicator information transmitted in the C-PDCCH or second C-PDCCH, anda UE operation therefor. The contents described in the variousembodiments of the disclosure are not limited to a specific embodiment,and may be applied to all of the embodiments of the disclosure.Therefore, unnecessary repetition of a description will be omitted byomitting a description of parts of the fourth embodiment that can beapplied and determined using the contents described in the first,second, and third embodiments.

FIG. 8 illustrates an operation of a base station according toembodiments of the disclosure.

The operation of the base station according to embodiments of thedisclosure will be described with reference to FIG. 8. In step 800, fora UE, the base station may configure, through a higher-layer signal, atleast one downlink control channel reception time or period andinformation (e.g. a time and frequency resource domain) about a resourcedomain in which the UE receives a downlink control channel. At least onedownlink control channel reception time or period of the downlinkcontrol channel reception time or periods may be defined in advancebetween the base station and the UE. In addition, a downlink controlchannel reception time or period for transmitting specific downlinkcontrol information in common to one or more UEs, such as cell-specificor cell-common or UE-group-common downlink control information, and adownlink control channel reception time or period for UE-specificdownlink control information transmission may be separately configuredby the downlink control channel reception time or period configurationinformation. At this instance, the two downlink control channelreception times or periods may be configured to be identical to ordifferent from each other. In step 800, the base station may configureone or more bandwidth parts to the UE, and may configure a downlinkcontrol channel reception time or period of each of the configuredbandwidth parts. Also, the base station can configure information (e.g.a time and frequency resource domain) on a resource domain in which theUE receives a downlink control channel in each of the configuredbandwidth parts.

Then, in step 810, the base station performs a channel access procedurefor an unlicensed band. The channel access procedure performed by thebase station in step 810 may be performed differently depending on thetype of signal to be transmitted in the unlicensed band, for example,whether a downlink data channel is included in the transmission orwhether an uplink data channel is included. For example, when a downlinkdata channel is not included in a signal to be transmitted by the basestation in an unlicensed band (i.e. when only a downlink control channelis transmitted), the channel access procedure may be different from thechannel access procedure when the downlink data channel is included in asignal to be transmitted by the base station in the unlicensed band.

The base station performs a channel access procedure for the unlicensedband in step 810 and determines in step 820 whether the unlicensed bandis an idle channel. When it is determined that the unlicensed band is anidle channel, the base station may transmit a downlink signal in theunlicensed band in step 830. At this time, the downlink signaltransmitted by the base station in the unlicensed band includes downlinkcontrol information including at least one piece of information on theuplink or downlink transmission interval within an interval in which thebase station is to occupy a channel. At this time, the information onthe uplink or downlink transmission interval refers to at least oneamong information on the length of an uplink or downlink transmissioninterval in a symbol or slot unit within the channel occupancy interval,information on an offset indicating a start symbol or slot of the uplinkor downlink transmission interval, or slot format indicator informationof at least one slot. In addition, when the downlink signal istransmitted in the unlicensed band, the base station may re-establish orchange the downlink control channel reception time or period of at leastone UE according to the method proposed by the disclosure, and maytransmit a downlink control channel according to the reconfigured orchanged downlink control channel reception time or period so as to allowthe UE to correctly receive the downlink control channel.

When it is determined in step 820 that the unlicensed band is not anidle channel, the base station may, in step 840, resume or continue thechannel access procedure for the unlicensed band without transmittingthe downlink signal in the unlicensed band or may change a band to alicensed band or another unlicensed band so as to communicate with theUE.

FIG. 9 is a flowchart illustrating an operation of a UE according toembodiments of the disclosure.

An operation of a UE according to the disclosure will be described withreference to FIG. 9. In step 900, the UE may receive a configuration forat least one downlink control channel reception time or period from abase station through a higher-layer signal. At least one downlinkcontrol channel reception time or period of the downlink control channelreception times or periods may be defined in advance between the basestation and the UE. In addition, a downlink control channel receptiontime or period for transmitting specific downlink control information incommon to one or more UEs, such as cell-specific or cell-common orUE-group-common downlink control information, and a downlink controlchannel reception time or period for transmission of UE-specificdownlink control information may be separately configured according tothe downlink control channel reception time or period configurationinformation. In this instance, the two downlink control channelreception times or periods may be configured to be identical to ordifferent from each other. In step 900, the UE may receive aconfiguration for one or more bandwidth parts from the base station, andmay receive a configuration for a downlink control channel receptiontime or period in each of the configured bandwidth parts. In thisinstance, information (e.g. a time and frequency resource domain) abouta resource domain in which the UE receives a downlink control channel ineach of the configured bandwidth parts may be configured.

In step 910, the UE receives a downlink control channel according to theconfigured downlink control channel reception time or period. In step920, the UE determines whether downlink control information has beentransmitted from the base station to the UE. When the UE receives, fromthe base station, downlink control information including at least onepiece of information on uplink or downlink transmission intervalinformation within an interval in which the base station is to occupythe channel, the UE, in step 930, reconfigures or changes the downlinkcontrol channel reception time or period according to the methodproposed by the disclosure, receives a downlink control channelaccording to the reconfigured or changed downlink control channelreception time or period, and determines whether the downlink controlinformation has been transmitted to the UE from the base station.

When the UE fails to receive, from the base station, downlink controlinformation including at least one piece of information on an uplink ordownlink transmission interval within an interval in which the basestation is to occupy the channel, the UE receives a downlink controlchannel according to the downlink control channel reception time orperiod configured in step 900, and determines whether the downlinkcontrol information has been transmitted from the base station to theUE. Here, the information on the uplink or downlink transmissioninterval refers to at least one among information on the length of anuplink or downlink transmission interval in a symbol or slot unit withinthe channel occupancy interval, information on an offset indicating astart symbol or slot of the uplink or downlink transmission interval, orslot format indicator information of at least one slot.

In order to perform the above-described embodiments of the disclosure, atransmitter, a receiver, and a processor of each of the UE and the basestation are illustrated in FIGS. 10 and 11. In order to perform theabove-described embodiments, the receiver, the processor, and thetransmitter of each of the base station and the UE operate according toeach embodiment.

Particularly, FIG. 10 is a block diagram illustrating the innerstructure of a base station according to an embodiment of thedisclosure. As illustrated in FIG. 10, the base station of thedisclosure may include a receiver 1000, a transmitter 1010, and aprocessor 1020. The receiver 1000 and the transmitter 1010 may becollectively referred to as a transceiver in an embodiment of thedisclosure. The transceiver may transmit and receive signals to and fromthe UE. The signal may include control information and data. To thisend, the transceiver may include an RF transmitter for up-converting andamplifying the frequency of a transmitted signal, an RF receiver forlow-noise amplifying a received signal and down-converting thefrequency, and the like. Further, the transceiver may receive a signalthrough a wireless channel, output the signal to the processor 1020, andtransmit the signal output from the processor 1020 through the wirelesschannel.

The processor 1020 may control a series of processes such that the basestation can operate according to the above-described embodiments of thedisclosure. For example, the receiver 1000 may receive a data signalincluding a control signal transmitted by the UE, and the processor 1020may determine the result of reception of the control signal and the datasignal transmitted by the UE. In another example, the processor 1020 mayperform a channel access procedure for an unlicensed band. For example,the receiver 1000 may receive signals transmitted in the unlicensedband, and the processor 1020 may compare the strength of the receivedsignal or the like based on a predetermined threshold value or the valueof a function predetermined or having a bandwidth, etc. as factors todetermine whether the unlicensed band is idle. When it is determinedthat the unlicensed band is idle, a downlink signal may be transmittedthrough the transmitter 1010. In this instance, the transmitter 1010 maytransmit, to a UE, information on an uplink or downlink transmissioninterval within the channel occupancy interval of the unlicensed banddetermined by the processor 1020.

FIG. 11 is a block diagram illustrating an internal structure of a UEaccording to an exemplary embodiment of the disclosure. As illustratedin FIG. 11, the UE of the disclosure may include a receiver 1100, atransmitter 1110, and a processor 1120. The receiver 1100 and thetransmitter 1110 may be collectively referred to as a transceiver in theembodiment of the disclosure. The transceiver may transmit and receive asignal to/from a base station. The signal may include controlinformation and data. To this end, the transceiver may include an RFtransmitter that up-converts and amplifies the frequency of atransmitted signal, an RF receiver that low-noise amplifies a receivedsignal and down-converts the frequency, and the like. Further, thetransceiver may receive a signal through a wireless channel, output thesignal to the processor 1120, and transmit the signal output from theprocessor 1120 through the wireless channel.

The processor 1120 may control a series of processes such that the UEcan operate according to the above-described embodiment of thedisclosure. For example, the receiver 1100 may receive a data signalincluding a control signal, and the processor 1120 may determine theresult of reception of the data signal. Thereafter, when a first signalreception result including the data reception should be transmitted tothe base station in the timing, the transmitter 1110 transmits, to thebase station, the first signal reception result in timing determined bythe processor. In another example, when the receiver 1100 receives, fromthe base station, information on an uplink or downlink transmissioninterval within a channel occupancy interval of an unlicensed band, theprocessor 1120 may reconfigure or change a downlink control channeltransmission time or period of the UE and thus the receiver 1100 mayreceive a downlink control channel transmitted by the base station.

Meanwhile, the embodiments of the disclosure disclosed in thespecification and the drawings have been presented to easily explaintechnical contents of the disclosure and help comprehension of thedisclosure, but do not limit the scope of the disclosure. That is, itwill be obvious to those skilled in the art to which the disclosurebelongs that other modifications based on the technical idea of thedisclosure are possible. Further, the above embodiments may be combinedwith each other as needed. For example, some of the methods proposed inthe disclosure may be combined with each other to operate the basestation and the UE. Although the above embodiments are presented basedon LTE and LTE-A systems, other modification examples based on thetechnical ideas of the above embodiments may be implemented in othersystems such as 5G and NR systems.

1. A method of a user equipment (UE) in a wireless communication system, comprising: monitoring a downlink control channel in an unlicensed band, based on a first period for the downlink control channel; in case that first downlink control information is received based on the first period, monitoring the downlink control channel, based on a second period for the downlink control channel; and receiving second downlink control information, based on the first downlink control information, wherein the first downlink control information relates to an occupancy interval of a base station.
 2. The method of claim 1, wherein the first downlink control information comprises at least one of multiple slot format indicators and information on a downlink transmission interval and an uplink transmission interval.
 3. The method of claim 1, wherein the second downlink control information is UE-specific control information.
 4. The method of claim 1, wherein the period for the downlink control channel is configured by higher-layer signaling, and the first control information comprises information on the second period for the downlink control channel.
 5. A method of a base station in a wireless communication system, comprising: performing a channel access procedure in an unlicensed band; in case that the unlicensed band is determined to be idle as a result of the channel access procedure, transmitting first downlink control information by using the unlicensed band on a downlink control channel, based on a first period for the downlink control channel; and transmitting second downlink control information by using the unlicensed band, based on a second period for the downlink control channel, wherein the first downlink control information relates to an occupancy interval of the base station.
 6. The method of claim 5, wherein the first downlink control information comprises at least one of multiple slot format indicators and information on a downlink transmission interval and an uplink transmission interval.
 7. The method of claim 5, wherein the second downlink control information is UE-specific information.
 8. The method of claim 5, wherein the period for the downlink control channel is configured by higher-layer signaling, and the first control information comprises information on the second period for the downlink control channel.
 9. A user equipment (UE) in a wireless communication system, comprising: a transceiver; and a controller coupled with the transceiver and configured to: monitor a downlink control channel in an unlicensed band, based on a first period for the downlink control channel; in case that first downlink control information is received based on the first period, monitor the downlink control channel, based on a second period for the downlink control channel; and receive second downlink control information, based on the first downlink control information, wherein the first downlink control information relates to an occupancy interval of a base station.
 10. The UE of claim 9, wherein the first downlink control information comprises at least one of multiple slot format indicators and information on a downlink transmission interval and an uplink transmission interval.
 11. The UE of claim 9, wherein the second downlink control information is UE-specific control information.
 12. The UE of claim 9, wherein the period for the downlink control channel is configured by higher-layer signaling, and the first control information comprises information on the second period for the downlink control channel.
 13. A base station in a wireless communication system, comprising: a transceiver; and a controller coupled with the transceiver and configured to: perform a channel access procedure in an unlicensed band; in case that the unlicensed band is determined to be idle as a result of the channel access procedure, transmit first downlink control information by using the unlicensed band on a downlink control channel, based on a first period for the downlink control channel; and transmit second downlink control information by using the unlicensed band, based on a second period for the downlink control channel, wherein the first downlink control information relates to an occupancy interval of the base station.
 14. The base station of claim 13, wherein the first downlink control information comprises at least one of multiple slot format indicators and information on a downlink transmission interval and an uplink transmission interval.
 15. The base station of claim 13, wherein the period for the downlink control channel is configured by higher-layer signaling, and the first control information comprises information on the second period for the downlink control channel. 